• Welcome to the new forum! We upgraded our forum software with a host of new boards, capabilities and features. It is also more secure.
    Jump in and join the conversation! You can learn more about the upgrade and new features here.

final gravity measurements?

Johnnyv42

Brewer
Joined
Oct 18, 2011
Messages
34
Reaction score
0
Location
Loveland, CO
I just checked the gravity of my Wee Heavy and it's much lower than my target. My recipe targeted 10% ABV and I'm only at about 7.5% :( I've not had this problem with previous batches of beer. I usually nail the ABV target right on the head. I'm wondering if my measurement is being fouled by the suspended particulate (yeast). When I taste it, it sure taste like a higher ABV than 7.5%, but that's so subjective (malt/hop/ethanol balance...). I've measured the gravity 2 different ways, using both my refractometer and my hydrometer, and get the same results. Is it possible that the suspended particulate/yeast are causing both tools to measure the gravity high?
 

MaltLicker

Forum Moderator
Grandmaster Brewer
Joined
Aug 25, 2008
Messages
2,004
Reaction score
0
Looking at what you've recently bottled, how often do you do 10% ABV brews?  Lautering efficiency drops with larger grain bills; if you did a 10% beer as all-grain, perhaps that was the issue? 

And with a wee heavy, one technique to boost the gravity is by a very long boil, so one does not have to collect all the OG from the grains. 

For ex, you may collect 1.085 and boil it down to 1.105 or so.  That also creates the caramelization flavors of the style. 
 

tom_hampton

Grandmaster Brewer
Joined
Oct 8, 2011
Messages
929
Reaction score
0
I think he's talking FG (not OG). 

10% is a strong beer.  Fermentations will stick or slow down as you go up in ABV%, and OG. 

How much yeast did you pitch?  You would have needed a LARGE starter for that beer: 4-ish liters without a stirplate, 2-ish with one.  Careful yeast selection is important, too.

Has your FG stopped moving?  If so, you can try to rouse the yeast: GENTLY stir it back into suspension. 

What temp are you fermenting at?  You can also try to warm it up some.  Warm slowly (a degree per hour is about right) to over 70F, you can probably go as high as 75F at this stage....depending on your yeast strain.
 

Johnnyv42

Brewer
Joined
Oct 18, 2011
Messages
34
Reaction score
0
Location
Loveland, CO
Thank you for your responses. Unfortunately, you're responding to a question I didn't ask. If the ABV is only 7.5% I have several ideas why that might be. My question refers to the measurement process itself, not the results of the measurement. I wouldn't be surprised if this beer didn't ferment as much as I would have liked. But I want to make sure that the cloudy beer isn't distorting the measurement some way. So, let me ask the question:

Does suspended particulate/yeast affect the refractometer measurement, does it affect the hydrometer measurement?

 

tom_hampton

Grandmaster Brewer
Joined
Oct 8, 2011
Messages
929
Reaction score
0
Does suspended particulate/yeast affect the refractometer measurement, does it affect the hydrometer measurement?

No.  Or rather, at the risk of providing to much detail, not enough to matter.
 

Johnnyv42

Brewer
Joined
Oct 18, 2011
Messages
34
Reaction score
0
Location
Loveland, CO
Detail? I like detail.  :) One of the things I like most about brewing is learning all the details. Would you like to share those unmentioned details? ...or at least a link to them.

Thanks!
 

Myk

Grandmaster Brewer
Joined
Apr 2, 2010
Messages
155
Reaction score
0
One detail is a dirty sample on a refractometer settles on the prism and blurs the line making it hard to read accurately.

That "feature" is one way to test corn for ripeness. Turn it upside down and the starch settles on the lid. But I found in brewing it's not a good test of conversion by comparing to iodine.
 

tom_hampton

Grandmaster Brewer
Joined
Oct 8, 2011
Messages
929
Reaction score
0
Johnnyv42 said:
Detail? I like detail.  :) One of the things I like most about brewing is learning all the details. Would you like to share those unmentioned details? ...or at least a link to them.

Thanks!

Dry weight of 20 billion yeast cells = 1gram.  A finished 5 gallon batch develops about 900 billion yeast cells = 45 grams = 1.6 oz.  If ALL of that were suspended (as opposed to being at the bottom of the carboy in the yeast cake), then that would increase the SG by 13 points.  Since 90% of the yeast is at the bottom of the carboy (not suspended), the SG impact is ~1/10th or 1.5 points.  That's one tick mark on your hydrometer, or about the deviation due to the meniscus.
 
Top